The resistance
of a wire changes if its lengthchanges.
This makes sense if you consider that there are anumber of collisions
between the electrons
and the ionswhen electricity flows through 1 metre of a wire.
There are twice as many collisions when electricityflows through 2 metres and 3 times as manycollisions when electricity flows through
3 metres etc.

If we plot
this on a graph
we get a
straight line relationship as shown
below.